Prior art impact devices incorporating a high speed rotary motor, gearing, and a single connecting rod, the latter positioned along the line of impacting and attached to the near end of a reciprocating body, necessarily have short connecting rods to avoid impractical lengths of the device. Typically such devices either have the motor offset from the line of impacting or incorporate a single cantilevered crank or split bearings, all of which generate serious problems including those caused by extraneous harmonics as described in my copending application Ser. No. 534,626, in which improved exciter-reciprocative drives are disclosed which either eliminate or reduce to insignificance such wasteful extraneous vibrations.